@suniuz noticed the detail that Mikasa reverses her 3DMG blade when Flocke approaches, flipping the sharper edge (The side of the hand pump) towards herself.
She was ready to hit him, but not kill him.
–
With that said, moments before Mikasa does lean the sharper edge of her blade against Levi’s neck. But as soon as he showed less resistance than she anticipated, she backed down and even asked him for the serum formally.
midnight-in-town 